There’s an old maxim about living in New York City: nobody knows their neighbours. The Wolfpack, a striking documentary from new film-maker Crystal Moselle, is just the thing to get people wondering what sociology experiments are happening in the apartment next door.

The six Angulo brothers (two of whom are twins) dress the same and all have long black hair. They and their (mostly off-screen) older sister are the children of Oscar and Susanne Angulo. The parents met when Susanne, midwestern hippy, went to Machu Picchu and fell in love with a new-agey tour guide. At the time, Oscar was into Krishna, and decided he wanted to breed, as his eldest calls it, “his own tribe”. The children all have Sanskrit names (Bhagavan, Govinda etc) and, despite living in somewhat cramped public housing on Manhattan’s Lower East Side, have almost never left their apartment. They get some air once or twice a year, but when they do, it is under strict parental supervision.

Oscar, who chooses not to work on philosophical grounds, feels the world is potentially unsafe, so prefers that his family stays home. The kids (who now age from 16 to 23) are homeschooled by their mother – she is compensated by the city for this; it’s the family’s sole income.

While the Angulo kids certainly behave unusually, they are not quite as cut off from mainstream culture as you may think. They gobble up DVDs, memorising films. Their primary creative output is to recreate scenes from their favourites such as Reservoir Dogs, The Nightmare Before Christmas and The Dark Knight. But they don’t just rattle off lines, they recreate sets, costumes and props with a remarkable craftiness. Indeed, their styrofoam guns were enough to spook someone to call the cops, thinking they were real.

While the kids, who all have wide smiles and deep voices, are bursting with kindness, it is clear there is tremendous unease roiling beneath the surface. These are smart, self-aware people, and they are trying to figure out how to leave the nest. It is implied that Oscar has been violent in the past, and now spends most of his time drinking in solitude – though it is quite difficult to find solitude in a dwelling so small.

Not since Grey Gardens has a film invited us into such a strange, barely-functioning home and allowed us to gawk without reservation. This is a nosy movie, but it is altogether fascinating. And, like Grey Gardens, it’s a story where every answer just spawns new questions. The Wolfpack won’t just “find an audience”, it will inspire people to revisit and peck for clues.

I suppose it isn’t too much of a spoiler to say that a degree of change comes to the family – they are the subjects of a vérité documentary after all. What will become of these people, and whether there are any silver linings to their conditioning, are questions ripe for post-screening debate. It has been a while since I’ve seen something that demands to be talked about with such urgency. In this regard, The Wolfpack is reminiscent of Capturing the Friedmans – it’s impossible not to have opinions.

Director Moselle’s touch is, by and large, a light one. She makes you work to root out points of backstory. The Wolfpack slowly reveals not just the Angulos’ “otherness”, but also the aspects that make them extraordinary. All are fabulous dressers, and, for young people who have barely socialised with other humans, are somewhat hammy. As they dance to the 1980s Europop anthem Tarzan Boy (and, yes, think on the implications of a song even loosely connected to that legend), there is a sense that good people can overcome adversity, even without a clear road map.

Sceptics may accuse Moselle of leaning on the noble savage cliche. I say any kid who has never known more than 15 feet of personal space, and can make a Batman costume out of old cereal boxes look that good, is well-deserving of our wonderment.